This article is from the Basic Health Care FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
Cavities in cat teeth often occur just at or under the gum line. If your cat has an infected tooth, you will have to have root work done on it. It is typical to do x-rays after such a procedure to ensure that all of the roots have reabsorbed. If the roots haven't done so, then the infection can easily continue on up to the sinus and nasal passages and from there to the lungs. Such infections require long-term antibiotics.
 
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